Numerous catalysts which can be used for the oxidative dehydrogenation of paraffinic hydrocarbons have already been reported in the literature. Thus, there may be mentioned mixed nickel and tin oxides (U.S. Pat. No. 3,745,294 and U.S. Pat. No. 3,801,671), mixed chromium and magnesium oxides (U.S. Pat. No. 3,801,672), and complex oxides combining a metal of group VIII with a metal of group VI B of the periodic table classification and, where appropriate, with a metal of group IV B or of group I A (U.S. Pat. Nos. 3,784,485 and 4,476,339).
West German Patent No. 1,800,063 discloses a process for obtaining mono- or diolefinic hydrocarbons by catalytic oxidative dehydrogenation of butane at a temperature of from 400.degree. to 700.degree. C., which is characterized in that the catalyst employed is a mixture of oxides comprising a molybdenum or tungsten oxide and at least one oxide of a metal chosen from chromium, manganese, iron, nickel and cadmium. This patent recommends, more particularly, the use of mixtures of oxides of molybdenum and nickel in a ratio of molybdenum to nickel of between 4 and 0.04. Example 1 of West German 1,800,063 illustrates the oxidative dehydrogenation of n-butane by means of a catalyst of this kind, obtained from aqueous solutions of ammonium molybdate and of nickel nitrate, which at 590.degree. C. results in a yield of 4.5% of n-butane and of 21% of butadiene. Example 2 of West German 1,800,063 shows that on carrying out the same reaction at 597.degree. C. with an atomic ratio of nickel to molybdenum equal to 0.68, the yields of butadiene and butenes which are obtained are lower than those obtained in Example 1 of the same patent with a Ni/Mo atomic ratio equal to 2.
Furthermore, U.S. Pat. No. 4,131,631 describes a process for dehydrogenation of paraffinic hydrocarbons containing from 3 to 6 carbon atoms to form the corresponding monoolefins, by bringing the hydrocarbon into contact with molecular oxygen, at a temperature of 400.degree. to 700.degree. C. and at a pressure of 1 to 3 atmospheres, over a catalyst of formula: EQU A.sub.a Co.sub.b Mo.sub.c O.sub.x
in which:
A is an element chosen from phosphorus and the metals of groups IA, IIA, VI and VIII of the periodic table classification, PA1 a is a number from 0 to 3, PA1 b is a number from 0.1 to 2, PA1 c is a number from 0.1 to 6, and PA1 x is a number determined by the valency requirements of the elements A, Co and Mo. PA1 a is a number approximately from 0.6 to 1.3, and PA1 x is a number determined by the valency requirements of PA1 nickel and of molybdenum. PA1 a is a number approximately from 0.6 to 1.3 and PA1 m and n are numbers dependent on the reaction conditions; and PA1 a is a number approximately from 0.6 to 1.3, by reaction of ammonium molybdate and of nickel nitrate.
More particularly, Example 8 of U.S. Pat. No. 4,131,631 describes a silica-supported Co.sub.0.5 Ni.sub.0.5 MoO.sub.x catalyst subjected to calcination at 593.degree. C. for 24 hours. This catalyst, employed for the oxidative dehydrogenation of propane at 538.degree. C. enables a pass conversion of 13.3% to be attained with a 63.9% selectivity for propylene, which results in a propylene yield of 8.5%. However, a catalyst of this type poses insoluble problems of reproducibility which are due to the presence of silica as the support, and has the disadvantage of an insufficient yield in the case of the oxidative dehydrogenation of propane. Furthermore, the length of its process of manufacture constitutes an obvious economic disadvantage.